Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2001-07-03
2002-11-05
Lavinder, Jack (Department: 3683)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C418S171000
Reexamination Certificate
active
06474752
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotary pump for sucking and discharging fluid and a braking apparatus using the rotary pump. In particular, the present invention is preferably applied to an internal gear pump such as a trochoid pump or the like.
2. Description of Related Art
There is a trochoid pump as one type of an internal gear rotary pump.
FIG. 22
shows such a trochoid pump. As shown by the drawing, the trochoid pump is constituted by an inner rotor
701
having an outer teeth portion
701
a
at its outer periphery, an outer rotor
702
having an inner teeth portion
702
a
at its inner periphery, a casing
704
for containing the outer rotor
702
and the inner rotor
701
. The inner rotor
701
and the outer rotor
702
are arranged in the casing
704
in a state where the inner teeth portion
702
a
and the outer teeth portion
701
a
are in mesh with each other and a plurality of gap portions
703
are formed by the respective teeth.
When a line running on respective central axes X′ and Y′ of the outer rotor
702
and the inner rotor
701
is defined as the center line Z′ of the pump, an intake port
705
and a discharge port
706
respectively communicating with the plurality of gap portions
703
are formed on both sides of the center line Z′. When the pump is driven, the inner rotor
701
rotates with the central axis Y′ as a drive axis. In accordance therewith, the outer rotor
702
also rotates in the same direction by mesh between the outer teeth portion
701
a
and the inner teeth portion
702
a
. In this case, each of the gap portions
703
changes from a large volume to a small volume and vice versa during a time period in which the outer rotor
702
and the inner rotor
701
make one turn. Due to that volume change, oil is sucked from the intake port
705
and discharged to the discharge port
706
.
In the internal gear pump such as a trochoid pump operating in this way, oil may leak from a clearance between the outer rotor
702
and the inner rotor
701
. The oil leakage is caused since the outer rotor
702
is separated from the inner rotor
701
and a clearance is produced at a gap portion of which the volume becomes its maximum among the plurality of gap portions
703
owing to a pressure difference between discharge pressure and intake pressure.
The gap portion of which the volume becomes its maximum, is a closed gap portion which communicates neither with the intake port
705
nor the discharge port
706
. Therefore, it maintains the pressure difference between the discharge pressure and the intake pressure and plays an important role in the pump smoothly carrying out intake and discharge operations. Accordingly, when the oil leakage as mentioned above happens, smooth pump operation cannot be carried out. For example, there arise problems such that a rotating unit is locked and high pressure oil cannot be discharged.
Hence, according to, for example, Japanese Unexamined Utility Model Publication No. JP-U-5-6170, oil leakage is prevented by reducing the clearance between the outer rotor
702
and the inner rotor
701
.
Specifically, a clearance L
1
between the outer rotor
702
and the casing
704
at a vicinity of the position where the volume of the gap portion becomes its maximum, is made smaller than a clearance L
2
between the outer rotor
702
and the casing
704
at a vicinity of the closed gap portion (having minimum volume) opposed to the closed gap portion having the maximum volume. As a result, the clearance between the outer rotor
702
and the inner rotor
701
at the closed gap portion having the maximum volume is prevented from widening. However, in this case, because of high pressure fluid leaking from the discharge port
706
to the outer periphery of the outer rotor
702
, the outer rotor
702
is pushed to a portion of the inner face of the casing
704
(point P) on the right side of the drawing.
Generally, the outer rotor
702
and the inner rotor
701
have fabrication errors in fabrication steps. Therefore, heights (length in diameter direction) of the teeth of the inner teeth portion
702
a
and heights (length in diameter direction) of the teeth of the outer teeth portion
701
a
are different from each other, respectively. Therefore, in setting clearances among a drive shaft, the inner rotor
701
, the outer rotor
702
and the casing
704
, the clearances are set by, for example, a method in which a maximum height tooth of the inner teeth portion
702
a
engages with a maximum height tooth of the outer teeth portion
701
a.
However, as mentioned above, heights of the teeth of the inner teeth portion
702
a
and the heights of the teeth of the outer teeth portion
701
a
are different from each other, respectively. Accordingly, when the closed gap portion having the maximum volume is formed by a tooth of the inner teeth portion
702
a
and a tooth of the outer teeth portion
701
a
which are shorter than the respective maximum height teeth thereof, a clearance is produced between the inner teeth portion
702
a
and the outer teeth portion
701
a
at the closed gap portion and oil leaks from the clearance.
Further, when the discharge pressure becomes high, force pushing the outer rotor
702
to the portion of the inner face of the casing
704
(vicinity of point P) on the right side of the drawing becomes large. Therefore, the pump may not be driven smoothly or the driving of the pump may be impossible since the outer rotor
702
are locked by being squeezed by the the casing
704
and the inner rotor
701
.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described problems and it is a first object of the present invention to provide a rotary pump capable of carrying out high pressure discharge by preventing fluid leakage and capable of being driven stably even when discharge pressure is high. Further, it is a second object of the present invention to provide a braking apparatus carrying out braking operation by using the rotary pump.
In a rotary pump according to a first aspect of the present invention, the outer rotor and the inner rotor are assembled in a casing such that, when a clearance between an inner teeth portion of an outer rotor and an outer teeth portion of an inner rotor is substantially nullified on a side of a first closed portion, which is a gap portion having a maximum volume, a clearance between the outer rotor and the casing on the outer periphery of the outer rotor on a side where the first closed portion is formed and a clearance between the outer rotor and the casing on a side where a second closed portion, which is the gap portion having a minimum volume is formed, become substantially an equivalent interval.
By such a constitution, an outer periphery of the outer rotor and an inner peripheral wall of the casing can be brought into contact with each other on the side of the second closed portion in view from the central axis of the inner rotor. Accordingly, even in a high pressure discharge operation, the outer rotor is not locked by being squeezed between the inner rotor and the casing and accordingly, the pump can be driven stably. Further, by torque transmitted from the inner rotor, the outer rotor is moved in a direction of contracting the clearance at the first closed portion. Accordingly, oil leakage between the outer teeth portion and the inner teeth portion at the first closed portion can be prevented.
Further, assembling operation may be carried out such that a clearance between the inner rotor and a drive shaft on the side where the first closed portion is formed may be set to be a half of the clearance between the inner rotor and the drive shaft.
The inner rotor and the outer rotor may be assembled in the casing such that a highest tooth portion of the inner teeth portion and a highest tooth portion of the outer teeth portion are disposed on a line defined by connecting the central axis of the outer rotor and the central axis of the inner rotor and on the side where the f
Harada Tomoo
Morikawa Toshiya
Yamaguchi Takahiro
Denso Corporation
Harness Dickey & Pierce PLC
Lavinder Jack
Williams Thomas J.
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